Enzymatic synthesis of optically active ferrocenes by immobilized lipase from Candida Antarctica

Immobilized lipase (Candida Antarctica lipase, CAL) efficiently catalyzes the transesterification and amidation of the racemic ferrocenes, 1-hydroxyethylferrocene, (+/-)-1, 1-hydroxy[3](1, 1') ferrocenophane, (+/-)-4, 1-amonoethylferrocene, (+/-)-2, and 1-amono[3](1,1') ferrocenophane, (+/-)-5, with acyl esters, resulting in the formation of R products possessing high enantiomeric purity. When 1-hydroxyethylferrocene, (+/-)-1, and 1-hydroxy[3](1,1') ferrocenophane, (+/-)-4, was used as substrate diisopropyl ether was a suitable solvent. In the reaction conditions investigated, the use of vinyl acetate in diisopropyl ether gave the best yield of (R)-1a (49%, 99% ee) after 2 h of incubation at 30 degrees C. But, with the amino ferrocenes, 1-amonoethylferrocene, (1)-2, and 1-amono[3](1,1') ferrocenophane, (+/-)-5, as substrate, diisopropyl ether was unsuitable as a solvent owing to the low solubility of the substrate in this solvent. Using tetrahydrofuran as a solvent, enzymatic amidation of 1-amonoethylferrocene, (+/-)2, gave the best yield of (R)-2a (21%, 99% ee) after 120 h of incubation at 30 degrees C. CAL working in organic solvent is able to efficiently carry out the resolution of ferrocenyl alcohol and amine derivatives which have similar structures, such as (+/-)-1 and (+/-)-2, (+/-)-4 and (+/-)-5 which possess central chirality. This enzyme accepted only non-bulky primary alcohols and amines as ferrocenyl substrates. (C) 1999 Society of Chemical Industry.